single cylinder and its 4 ports shown in this article
represents about 5 hours work. admittedly it was my first
attempt at porting so i took things a little slow, and was
probably over cautious, but in the words of a professional
head porter "fuckin time consuming isn't it!".
the images below demonstrate the approaches i took to
porting the short walled (casting #11) 7mge head. i've
tried to take the images as best as possible to show the
areas of most interest. each series of images represents
the worked port, followed by its stock equivalent, and
i've tried my best to keep the proportions between the
images consistent so you can see the effects more clearly.
see the captions below each image for a full description.
for a comprehensive
technical introduction to the principals head porting, and
a practical guide to head porting techniques, see the
links page available from the main menu.
above:: oblique view of the intake ports. things to
note include: removal of the machined shoulder present
below the seats in both ports- a results of factory valve
seat installation. grinding of the seat itself, right up
to the 45deg angle of the seat shoulder. significant
rounding, blending and smoothing of the short side radius.
blending and radiusing of the port divider. this divider
was also narrowed slightly at its leading edge, but not
significantly, leaving it rather blunt.
above:: this low view of the intake best shows the
improvements made in the short side radius' curve and
contour. notice how bad the machined shoulders are below
the seats in the stock port. it is also a good view to
note how the seats themselves have been ground right up to
the 45deg cut (note the shine).
above:: despite these two images being in slightly
different proportions, you might get some idea how much
larger the worked ports now are. its also a good view to
appreciate how the bowl has been blended into the valve
guide base, how the roof and walls have been contoured
around the 'ramp' leading up to the valve guide, and how
the guide itself has been countoured. you may also notice
that the 2 'mounds' on either side of the valve guide in
the stock port have been removed, and blended into the
roof and bowl.
above:: this shot of the bowl basically shows a
mild increase in bowl volume, but far better blending,
both at the seat, and with the valve guides. its also a
good view to appreciate the grind up to the 45deg cut on
the valve seat, and the overall increase in port size.
notice the small steps present in the valve seat in the
above:: exhaust port main view. note the knife
edging on the finished divider, this is an effort to
reduce turbulence as the two air streams come back
above:: low angle exhaust valve port view, again,
note the LARGE increase in port diameter, as well as the improvement of the
short side radius - in particular, the removal of that obvious machined step.
above:: directly above, exhaust port valve view.
note the blending of the stem guide rof, and the tapering of the guide tips
above:: exhaust valve port bowl view. of interest
here is the quality of the bowl area, and its transition around the valve guide.
you can also see the obvious step that existed underneath the original valve
seats (+1mm) which has been blended smooth - this has resulted in opening up the
ex valve port diameters by around 2mm.
You're a tool....
a few people have asked me specifically
what tools did i use for the above work, and so here she
is, my friend and yours, the dremel. 37,000 rpm of 'knife
through butter' cutting and grinding joy. the key with the
dremel and the following bits is TAKE IT SLOW- the cutting
pieces can chew straight into the alloy before you know
recently, ive actually been looking at using some burring dental
tools available from dental supply places -for dentists,
der- they have a massive variety of types and shapes, and
are cheaper than dremel parts also.
for more information regarding the types of dremel cutters
available, check out: